Many drugs mediate their effects on cells by interacting with (e.g., binding) nucleic acid sequences in cells. Interactions of drugs with nucleic acid sequences in cells (e.g., DNA of a cancerous cell) can stop cellular proliferation or cause cell death, thereby halting the progression of a disease state. However, many drugs employed to treat diseases are either insufficiently soluble in aqueous solutions or have adverse side effects, such as the death of healthy cells, because of the lack of suitable substances to deliver drugs to a cell or organism (e.g., mammal) requiring treatment.
There have been many attempts to overcome problems generally associated with drug delivery. For example, macromolecular drug-carriers, which most commonly are water-soluble macromolecules with chemically associated drug molecules, often are employed to prolong drug circulation, limit renal clearance, increase drug accumulation in target tissues or cells, and to decrease drug concentration in normal tissues. Several model and prototype carriers of this type have been developed. Potentially, these carriers can be as small as 5-10 nanometers (nm), but depending on the drug structure and content, they often form larger (20-50 nm) associates. Carriers of this type are intended to act, essentially, as pro-drugs, the drug substance as a result of degradation of the drug-carrier bond. Some carriers of this type have been targeted to cancer cell markers. Examples of this class of drug-carriers are: dextran-mitomycin conjugates; HPMA-doxorubicin conjugates with enzyme-degradable peptide bonds between the drug molecule and the backbone polymer; doxorubicin-Fab conjugates with pH-sensitive bonds between doxorubicin molecules and the Fab. Although potentially useful, carriers of this type have at least two potential drawbacks.
First, drug release via degradation of the drug-carrier bond generally is irreversible. Thus, drug released from the carrier will circulate in the body independently of the carrier, which may reduce the efficacy of drug delivery. Drug release via enzyme-dependent or pH-dependent hydrolysis has been reported to improve the ratio of drug activity in the target relative to normal tissues. However, expression of enzymes, such as proteases, in tumors and other pathologies is highly variable, which makes predictability of release rate of the drug difficult. Enzyme-independent biodegradation, on the other hand, can occur in both pathological and normal tissues.
A second problem relates to exposure to the environment of drug molecules attached to the macromolecular backbone. This can result in cross-interaction of drug moieties with formation of intramolecular and intermolecular micelles, interactions with tissue components altering drug-carrier adduct biodistribution, and other undesirable effects. These effects are expected to be partially suppressed via xe2x80x9csteric protection,xe2x80x9d or modification of the carrier backbone with hydrophilic polymer chains such as, for example, polyethyleneglycol, dextran, or PHF (polyhydroxymethylethylene hydroxymethylformal). However, in sterically protected carriers, enzyme access to enzyme-sensitive drug-carrier bonds also may be suppressed.
Another attempt to overcome problems associated with drug delivery includes combination of drugs with microparticles and emulsions. Microparticles and emulsions were developed as an alternative where the drug molecules are not bound chemically, but rather are adsorbed on, or dissolved in, the material of the carrier. However, particles and emulsions do not circulate in vivo long enough and accumulate in the reticuloendothelial system (RES) and other organs, unless the particle (droplet) surface is modified with a hydrophilic polymer, such as PEG. The overall size of sterically protected particles (droplets) is usually above about 25 nm. Major problems in the development of such carriers include the fact that (1) the emulsions generally are relatively unstable and change (e.g. coalesce) in storage; (2) high-scale production of both submicron particles and emulsions typically is difficult; and (3) drug molecules released from the particles or droplets will circulate independently of the carrier. Emulsions and most particles are not suitable for transport of hydrophilic drugs.
A specific development in drug delivery was employment of micelles, which were developed as xe2x80x9cself-assemblingxe2x80x9d drug carriers similar to particles and emulsions. They are made of surfactants, which are usually block copolymers, where one of the blocks is hydrophilic, and the other hydrophobic. The total hydrodynamic size of the micelles usually is 10-30 nm. The hydrophobic drug molecules either are incorporated into the hydrophobic core or, alternatively, chemically conjugated with one of the blocks and form the hydrophobic core. Some of the problems in the development of such carriers are similar to those described above. In addition, none of these carriers can reabsorb specifically the released drug; drug release rate is difficult to control, and amphiphylic components can produce toxic effects. These carriers are not suitable for transport of hydrophilic drugs.
Still another attempt includes encapsulation of drugs in the aqueous compartments of liposomes, which are vesicles, typically having a diameter in a range of between about 50 and about 1000 nm. However the efficacy of drug encapsulation and the potential to control drug delivery by incorporation into liposomes can be problematic. For example, drug release from liposomes generally is irreversible. Further, liposome penetration into tumors or tumor zones that have relatively low vascular permeability often is poor. Also, there are many problems associated with high-volume production and storage of liposomal preparation that present significant technical challenges.
Other systems employed to bind drugs for delivery to a cell or an organism have similar drawbacks. Thus, there is a need for a method to deliver drugs that minimize or overcome the above-referenced problems.
The present invention relates to the field of drug delivery, in particular to methods of forming drug-carrier complexes and the use of drug-carrier complexes as pharmaceutical compositions to deliver and target drugs in an organism, tissue culture or cells.
In one embodiment, the method includes forming a drug-carrier complex by combining at least one nucleotide strand with a drug, whereby the drug and the nucleotide strand reversibly associate with each other to form a drug-carrier complex.
In another embodiment, the method includes forming a drug-carrier complex by combining a drug with at least two nucleotide strands that hybridize with each other, whereby the drug associates with the nucleotide strands to form a water soluble drug-carrier complex.
In still another embodiment, the method includes forming a drug-carrier composition by combining a drug component and a nucleotide component. The combined drug and nucleotide components are lyophilized to form the drug-carrier composition.
In yet another embodiment, the method includes forming a drug-carrier composition by lyophilizing a drug component, lyophilizing a nucleotide component and combining the lyophilized drug component and the lyophilized nucleotide component to form the drug-carrier composition.
Another embodiment of the invention is a drug carrier, comprising a double-stranded nucleotide and a polymer component covalently bonded to at least one strand of the double-stranded nucleotide. The polymer component has an aqueous solubility of at least one mg/liter at 25xc2x0 C.
An additional embodiment of the invention is a drug carrier, comprising a double-stranded nucleotide and an oligomer component covalently bonded to at least one strand of the double-stranded nucleotide.
In an additional embodiment, the invention is a drug-carrier complex, comprising a single-stranded nucleotide, a drug reversibly associated with the single-stranded nucleotide and a polymer associated with the drug or the single-stranded nucleotide.
In yet another embodiment, the invention is a drug-carrier complex, comprising a single-stranded nucleotide, an oligomer associated with the single-stranded nucleotide and a drug reversibly associated with the oligomer or the single-stranded nucleotide.
In still another embodiment, the invention is a drug carrier, comprising a single-stranded nucleotide and at least two polymers associated with the single-stranded nucleotide.
In another embodiment, the invention is a drug carrier, comprising an oligomer, a single-stranded nucleotide entrapped by the oligomer and a drug reversibly associated with the single-stranded nucleotide.
In still another embodiment, the invention is a drug-carrier composition, comprising a nucleotide carrier component and a drug component. The drug-carrier composition has a moisture content less than about 5% by weight.
In yet another embodiment, the invention includes a drug-carrier composition consisting essentially of a drug component and a nucleotide component.
In an additional embodiment, the invention is a pharmaceutical formulation, comprising a nucleotide carrier component and a drug in reversible association with the nucleotide carrier component.
In still another embodiment, a method of the invention includes delivering a drug to an organism by administering a drug-carrier complex to the organism. The drug-carrier complex includes a nucleotide carrier and a drug in reversible association with each other.
In another embodiment, a method of the invention includes delivering a drug to a tissue culture by administering a drug-carrier complex to the tissue culture. The drug-carrier complex includes a nucleotide carrier and a drug in reversible association with each other.
In yet another embodiment, the method includes delivering a drug to an organism by administering a drug and a nucleotide carrier, which reversibly associates with the drug to form a drug-carrier complex, to the organism.
In still another embodiment, the method includes delivering a drug to an organism by forming a drug carrier complex that includes a drug and a nucleotide strand in reversible association with the drug and administering the drug-carrier complex to the organism.
Another embodiment includes a method of delivering a drug to an organism by administering to the organism a drug-carrier complex. The drug-carrier complex includes a drug component and a carrier component in reversible association with each other. The drug can dissociate from the drug-carrier complex and reassociate with the carrier component. The degree of association can depend, for example, on the concentrations of the drug and the carrier.
In still another embodiment, the method includes increasing aqueous solubility of a substance by reversibly associating the substance with a nucleotide carrier to form a water-soluble complex.
In yet another embodiment, the invention is a targeted carrier, comprising a nucleotide, a polymer component associated with the nucleotide, and a ligand associated with the nucleotide or the polymer component and associable with a cell or tissue marker. The cell or tissue marker is selected from the group consisting of proteins, peptides, carbohydrates, lipids and nucleotides.
In still another embodiment, the invention relates to a targeted carrier, comprising a nucleotide, a polymer component associated with the nucleotide and a ligand. The ligand is associated with the nucleotide or the polymer component and is associable with a cell or tissue marker. The cell or tissue marker is selected from the group consisting of proteins, peptides, carbohydrates, lipids and nucleotides.
In an additional embodiment, the invention relates to a targeted drug-carrier complex, comprising a nucleotide, a drug reversibly associated with the nucleotide and a targeting component. The targeting component is associated with the nucleotide or the drug. The targeting component includes a ligand associable with a cell or tissue marker. The cell or tissue marker is selected from the group consisting of proteins, peptides, carbohydrates, lipids and nucleotides.
In yet another embodiment, the invention relates to a targeted drug-carrier complex, comprising a nucleotide, a drug reversibly associated with the nucleotide, a polymer component associated with the nucleotide or the drug and a targeting component. The targeting component is associated with the nucleotide, the drug or the polymer. The targeting component includes a ligand associable with a cell or tissue marker. The cell or tissue marker is selected from the group consisting of proteins, peptides, carbohydrates, lipids and nucleotides.
In an additional embodiment, the invention relates to a drug delivery system, comprising a matrix, a nucleotide associated with or entrapped within the matrix and a drug in reversible association with the nucleotide.
Another embodiment includes an implant, comprising an implant matrix, a nucleotide associated with or entrapped within the matrix and a drug in reversible association with the nucleotide.
The invention described herein provides drug-carrier complexes, drug-carrier compositions, drug carriers, pharmaceutical formulations, methods of delivery drugs to organisms and tissue cultures, targeted carriers and implants to deliver drugs to an organism, a tissue culture or a combination of cells. The nucleotide-based drug delivery systems of the present invention have many advantages. For example, they can transport drugs in chemically unmodified form, and can reabsorb the released drug. By employing a reversible drug association, the drug delivery systems of this invention are able to reincorporate the released drug. Thus, drug behavior in the tissues may remain dependent on the drug release system for as long as the latter remains functional, which offers the possibility of new opportunities in regulation of pharmacokinetics and pharmacodynamics. In a clinical setting, this is expected to result in better biological functionality and broader safety margins of pharmaceutical formulations and devices.
Other advantages include, for example, a relatively small size of the drug-carrier complex, such as, for example, about 3 or about 5 nm. The drug-carrier complex can be, for example, 5 to 10 times smaller than polymer- and micelle-based carriers, and at least 10 to 20 times smaller than liposomes. Therefore, drug penetration into certain tissues, such as cancerous tissues, may be significantly more efficient, especially where endothelial and interstitial barriers are high. Also, stability and release rates of drug-carrier complexes of the invention can be controlled within a broad range, thereby providing the opportunity to design products in accordance with specific clinical objectives. Further, release of drugs by the drug-carrier complexes of the invention does not require interactions with enzymes, cells or other factors, thereby making the drug-carrier complexes more independent of the organism and tissue state. Alternatively, however, complexes of the invention can be designed to exploit specific conditions of an organism or tissue state, such as pH or enzyme content. In addition, the components of the drug-carrier complexes of the invention can be made of close analogs of natural components of biological systems which are known to be completely biodegradable and non-toxic.
Other specific advantages of the invention include the possibility of steric protection against carrier clearance and drug inactivation. Also, the drug-carrier complexes of the invention generally have no problems relevant to intramolecular or intermolecular association of drug molecules. Further, methods of forming and processing the drug-carrier complexes of the invention are readily scalable. Also, drug-carrier complexes are lyophilizable, and all components of the complexes can be stable in the presence of air. Further, no toxic surfactants are employed, the size of the complexes generally is stable and does not depend on conditions and concentration. Drug release rate within an organism generally does not depend on highly variable adsorption forces. Ultrafiltration typically does not affect size and structure of the drug-carrier complexes.